Knife deployment mechanisms for surgical forceps

ABSTRACT

A surgical instrument includes an end effector assembly having jaw members movable between spaced-apart, first approximated, and second approximated positions. A knife is selectively movable relative to the end effector assembly between a retracted position, a first extended position, and a second extended position. A trigger is selectively actuatable between a un-actuated position, a first actuated position, and a second actuated position for moving the knife between its respective positions. A control member prevents movement of the trigger when the jaw members are disposed in the spaced-apart position, permits movement of the trigger to the first actuated position but prevents movement beyond the first actuated position when the jaw members are disposed in the first approximated position, and permits movement of the trigger to the second actuated position but prevents movement beyond the second actuated position when the jaw members are disposed in the second approximated position.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation application of U.S. patentapplication Ser. No. 14/795,290, filed on Jul. 9, 2015, which is acontinuation application of U.S. patent application Ser. No. 14/299,740,filed on Jun. 9, 2014, now U.S. Pat. No. 9,084,608, which is acontinuation application of U.S. patent application Ser. No. 13/400,290,filed on Feb. 20, 2012, now U.S. Pat. No. 8,747,434, the entire contentsof each of which are incorporated herein by reference.

BACKGROUND Technical Field

The present disclosure relates to surgical instruments and, moreparticularly, to knife deployment mechanisms for use with surgicalforceps for grasping, treating, and/or dividing various tissuestructures.

Background of Related Art

A forceps is a plier-like instrument which relies on mechanical actionbetween its jaws to grasp, clamp and constrict vessels or tissue.Electrosurgical forceps utilize both mechanical clamping action andelectrical energy to affect hemostasis by heating tissue and bloodvessels to coagulate and/or cauterize tissue. Certain surgicalprocedures require more than simply cauterizing tissue and rely on theunique combination of clamping pressure, precise electrosurgical energycontrol and gap distance (i.e., distance between opposing jaw memberswhen closed about tissue) to “seal” tissue, vessels and certain vascularbundles. Typically, once a vessel is sealed, the surgeon has toaccurately sever the vessel along the newly formed tissue seal.Accordingly, many vessel sealing instruments have been designed whichincorporate a knife or blade member which effectively severs the tissueafter forming a tissue seal.

SUMMARY

As used herein, the term “distal” refers to the portion that is beingdescribed which is further from a user, while the term “proximal” refersto the portion that is being described which is closer to a user.Further, to the extent consistent, any of the aspects described hereinmay be used in conjunction with any of the other aspects describedherein.

A surgical instrument provided in accordance with the present disclosureincludes an end effector assembly having first and second jaw members.One or both of the jaw members is movable relative to the other betweena spaced-apart position, a first approximated position defining a firstgap distance therebetween, and a second approximated position defining asecond gap distance therebetween. A knife is selectively movablerelative to the end effector assembly between a retracted position, afirst extended position, in which the knife extends between the jawmembers a first distance, and a second extended position, in which theknife extends between the jaw members a second distance. A trigger isselectively actuatable between a un-actuated position, a first actuatedposition, and a second actuated position for moving the knife betweenthe retracted position, the first extended position, and the secondextended position, respectively. One or more control members is operablycoupled to the trigger. The control member(s) is configured to preventmovement of the trigger from the un-actuated position when the jawmembers are disposed in the spaced-apart position. The control member(s)is further configured to permit movement of the trigger from theun-actuated position to the first actuated position and prevent movementof the trigger beyond the first actuated position when the jaw membersare disposed in the first approximated position. The control member(s)is also configured to permit movement of the trigger from theun-actuated position to the second actuated position and preventmovement of the trigger beyond the second actuated position when the jawmembers are disposed in the second approximated position.

In one aspect, the surgical instrument includes a drive assembly coupledto one or both of the jaw members. The drive assembly includes a mandrelthat is selectively translatable between a first position, a secondposition, and a third position for moving the jaw members between thespaced-apart position, the first approximated position, and the secondapproximated position, respectively.

In another aspect, the surgical instrument includes a movable handlecoupled to the mandrel. The movable handle is movable between an initialposition, a first compressed position, and second compressed positionfor moving the jaw members between the spaced-apart position, the firstapproximated position, and the second approximated position,respectively.

In yet another aspect, a first control member is engaged to the mandreland is movable therewith. In the first position, the first controlmember interferes with the trigger to prevent actuation of the triggerfrom the un-actuated position. In the second position, the first controlmember permits movement of the trigger from the un-actuated position tothe first actuated position but interferes with the trigger to preventactuation of the trigger beyond the first actuated position. In thethird position, the first control member permits movement of the triggerfrom the un-actuated position to the second actuated position butinterferes with the trigger to prevent actuation of the trigger beyondthe second actuated position.

In still another aspect, a second control member is coupled to thetrigger. The second control member is operable to engage the firstcontrol member to prevent actuation of the trigger from the un-actuatedposition when the jaw members are disposed in the spaced-apart position.The second control member is further operable to prevent actuation ofthe trigger beyond the first actuated position when the jaw members aredisposed in the first approximated position. The second control memberis also operable to prevent actuation of the trigger beyond the secondactuated position when the jaw members are disposed in the secondapproximated position.

In yet another aspect, the control member includes an elongated bodyhaving a plurality of spaced-apart protrusions extending therefrom. Theelongated body is movable, upon movement of the mandrel between thefirst, second, and third positions, between a first blocking position,wherein a first protrusion prevents actuation of the trigger from theun-actuated position, a second blocking position, wherein a secondprotrusion prevents actuation of the trigger beyond the first actuatedposition, and a third blocking position, wherein a third protrusionprevents actuation of the trigger beyond the second actuated position.

In still yet another aspect, one or both of the jaw members includes aknife channel defined therein. The knife channel is configured to permitreciprocation of the knife therethrough. More specifically, when the jawmembers are disposed in the first approximated position, a relativelysmaller portion of the knife is disposed within the knife channel(s)during extension of the knife between the jaw members. On the otherhand, when the jaw members are disposed in the second approximatedposition, a relatively greater portion of the knife is disposed withinthe knife channel(s) during extension of the knife between the jawmembers.

Another surgical instrument provided in accordance with the presentdisclosure includes an end effector assembly having first and second jawmembers. One or both of the jaw members is movable relative to the otherbetween a spaced-apart position, a first approximated position defininga first gap distance therebetween, and a second approximated positiondefining a second gap distance therebetween. A knife is selectivelymovable relative to the end effector assembly between a retractedposition, a first extended position, in which the knife extends betweenthe jaw members a first distance, and a second extended position, inwhich the knife extends between the jaw members a second distance. Atrigger is selectively actuatable between a un-actuated position, afirst actuated position, and a second actuated position for moving theknife between the retracted position, the first extended position, andthe second extended position. The trigger has a resistance associatedwith moving the trigger. One or more control members is operably coupledto the trigger. The control member(s) is configured to provide a firstadditional resistance to movement of the trigger upon movement of thetrigger from the un-actuated position when the jaw members are disposedin the spaced-apart position. The control member(s) is furtherconfigured to provide a second additional resistance to movement of thetrigger upon movement of the trigger beyond the first actuated positionwhen the jaw members are disposed in the first approximated position.The control member(s) is also configured to provide a third additionalresistance to movement of the trigger upon movement of the triggerbeyond the second actuated position when the jaw members are disposed inthe second approximated position.

In one aspect, the first, second and third additional resistancesprovide tactile feedback to a user actuating the trigger.

In another aspect, the surgical instrument includes a drive assemblycoupled to one or both of the jaw members. The drive assembly includes amandrel that is selectively translatable between a first position, asecond position, and a third position for moving the jaw members betweenthe spaced-apart position, the first approximated position, and thesecond approximated position, respectively.

In yet another aspect, a first control member is operably coupled to themandrel and is movable therewith. In the first position, the firstcontrol member is positioned to provide the first additional resistanceupon movement of the trigger from the un-actuated position. In thesecond position, the first control member is positioned to provide thesecond additional resistance upon movement of the trigger beyond thefirst actuated position. In the third position, the first control memberis positioned to provide the third additional resistance upon movementof the trigger beyond the second actuated position.

In still another aspect, a second control member is coupled to thetrigger. The second control member is operable to engage the firstcontrol member to provide the first additional resistance, the secondadditional resistance, and the third additional resistance.

In yet another aspect, one or both of the control members is configuredto provide audible feedback upon engagement of the first and secondcontrol members.

In still yet another aspect, the control member includes an elongatedbody having a plurality of spaced-apart protrusions extending therefrom.The elongated body is movable, upon movement of the mandrel between thefirst, second, and third positions, between a first blocking position,wherein a first protrusion provides the first additional resistance tothe trigger, a second blocking position, wherein a second protrusionprovides the second additional resistance to the trigger, and a thirdblocking position, wherein a third protrusion provides the thirdadditional resistance to the trigger. One or more of the first, second,and third protrusions may be formed from a resiliently-flexiblematerial.

In another aspect, the surgical instrument includes a movable handleoperably coupled to one or both of the jaw members. The movable handleis movable between an initial position, a first compressed position, andsecond compressed position for moving the jaw members between thespaced-apart position, the first approximated position, and the secondapproximated position, respectively.

In still yet another aspect, one or both of the jaw members includes aknife channel defined therein. The knife channel is configured to permitreciprocation of the knife therethrough. More specifically, when the jawmembers are disposed in the first approximated position, a relativelysmaller portion of the knife is disposed within the knife channel(s)during extension of the knife between the jaw members. On the otherhand, when the jaw members are disposed in the second approximatedposition, a relatively greater portion of the knife is disposed withinthe knife channel(s) during extension of the knife between the jawmembers.

BRIEF DESCRIPTION OF THE DRAWINGS

Various aspects of the present disclosure are described herein withreference to the drawings wherein like reference numerals identifysimilar or identical elements:

FIG. 1 is a side, perspective view of a forceps provided in accordancewith the present disclosure;

FIG. 2A is a side, perspective view of a distal end of the forceps ofFIG. 1 wherein jaw members of the forceps are disposed in a spaced-apartposition;

FIG. 2B is a side, perspective view of the distal end of the forceps ofFIG. 1 wherein the jaw members of the forceps are disposed in anapproximated position;

FIG. 3 is a side, perspective view of the distal end of the forceps ofFIG. 1 shown with parts separated;

FIG. 4A is a side, perspective view of a proximal end of the forceps ofFIG. 1 wherein a portion of a housing has been removed to show theinternal components thereof;

FIG. 4B is a side, perspective view of the proximal end of the forcepsof FIG. 1 with a portion of the housing removed with parts separated;

FIG. 5 is a side, cut-away view of the forceps of FIG. 1 wherein ahandle assembly is disposed in an initial position, a trigger assemblyis disposed in an un-actuated position, and the jaw members are disposedin the spaced-apart position;

FIG. 6 is a side, cut-away view of the forceps of FIG. 1 wherein thehandle assembly is disposed in a first compressed position, the triggerassembly is disposed in an un-actuated position, and the jaw members aredisposed in a first approximated position;

FIG. 6A is a transverse, cross-sectional view of the jaw members of theforceps of FIG. 1 disposed in the first approximated position graspingtissue therebetween, wherein a knife has been advanced between the jawmembers to cut tissue grasped therebetween;

FIG. 6B is a side view of the jaw members of the forceps of FIG. 1disposed in the first approximated position and including the knifeextending partially therebetween;

FIG. 7 is a side, cut-away view of the forceps of FIG. 1 wherein thehandle assembly is disposed in a second compressed position, the triggerassembly is disposed in an un-actuated position, and the jaw members aredisposed in a second approximated position;

FIG. 7A is a transverse, cross-sectional view of the jaw members of theforceps of FIG. 1 disposed in the second approximated position graspingtissue therebetween, wherein the knife has been advanced between the jawmembers to cut tissue grasped therebetween;

FIG. 7B is a side view of the jaw members of the forceps of FIG. 1disposed in the second approximated position and including the knifeextending therebetween;

FIG. 8 is a side, cut-away view of another forceps provided inaccordance with the present disclosure;

FIG. 9 is a side, cut-away view of another forceps provided inaccordance with the present disclosure wherein a handle assembly isdisposed in an initial position and wherein a trigger assembly isdisposed in an un-actuated position; and

FIG. 10 is a side, cut-away view of the forceps of FIG. 9 wherein thehandle assembly is disposed in a compressed position and wherein thetrigger assembly is disposed in an actuated position.

DETAILED DESCRIPTION

The operating features and inter-cooperating components of a surgicalinstrument provided in accordance with the present disclosure are shownin the Figures and described hereinbelow. More specifically, thesurgical instrument is shown as a forceps 10, although the presentdisclosure is equally applicable for use with any surgical instrumenthaving a handle assembly operable to control and/or manipulate an endeffector assembly of the surgical instrument and a trigger assemblyoperable to deploy a knife for cutting tissue grasped by the endeffector assembly. Obviously, different connections and considerationsapply to each particular type of instrument; however, the novel aspectswith respect to the handle assembly, trigger assembly, and theinteraction therebetween remain generally consistent regardless of theparticular type of instrument used. For the purposes herein, forceps 10is generally described.

Referring to FIG. 1, forceps 10 is configured for use in varioussurgical procedures and includes a housing 20, a handle assembly 30, aswitch assembly 60, a trigger assembly 70, a rotating assembly 80, andan end effector assembly 100 that mutually cooperate to grasp, treat,and divide tubular vessels and vascular tissues. Forceps 10 furtherincludes a shaft 12 having a distal end 16 configured to mechanicallyengage end effector assembly 100 and a proximal end 14 configured tomechanically engages housing 20. An electrosurgical cable 2 connectsforceps 10 to an electrosurgical generator (not shown) such that, uponactivation of switch 62 and/or switch 64 of switch assembly 60, energyis supplied to end effector assembly 100 to treat tissue graspedtherein, as will be described in greater detail below. Alternatively,forceps 10 may be configured as a battery-powered instrument having aportable battery (not shown) and generator (not shown) disposed withinhousing 20.

Handle assembly 30 includes a fixed handle 50 and a movable handle 40.Fixed handle 50 is integrally associated with housing 20 and handle 40is movable relative to fixed handle 50, as will be explained in greaterdetail below, to impart movement of jaw members 110 and 120 of endeffector assembly 100 between a spaced-apart position (FIG. 2A) and oneor more approximated positions (FIG. 2B) to grasp tissue therebetween.Rotating assembly 80 is operatively associated with housing 20 and isrotatable about a longitudinal axis “A-A” to rotate end effectorassembly 100 about longitudinal axis “A-A.” Trigger assembly 70, as willbe described in greater detail below, is selectively actuatable todeploy a knife 190 (FIG. 3) from shaft 12 to between jaw members 110,120 to cut tissue grasped therebetween.

With additional reference to FIGS. 2A-2B and 3, end effector assembly100 is attached at distal end 16 of shaft 12 and includes a pair ofopposing jaw members 110 and 120. End effector assembly 100 is designedas a bilateral assembly, i.e., both jaw members 110 and 120 are movablerelative to one another and shaft 12 about a pivot pin 95, although endeffector assembly 100 may alternatively be configured as a unilateralend effector assembly. Further, jaw members 110 and 120 of end effectorassembly 100 are curved to facilitate manipulation of tissue and toprovide better “line of sight” for accessing targeted tissues, althoughother configurations may also be provided.

With particular reference to FIG. 3, each jaw member 110, 120 includes adistal jaw portion 111, 121 that supports an electrically-conductivetissue sealing plate 112, 122, respectively, thereon, and a proximalflange 113, 123 extending distally from the respective distal jawportion 111, 121 thereof for operably mounting jaw members 110, 120,respectively, at distal end 16 of shaft 12. Either or bothelectrically-conductive tissue sealing plates 112, 122 are adapted toconnect to a source of energy, e.g., a generator (not shown), forconducting energy therebetween and through tissue grasped between jawmembers 110, 120 to treat, e.g., seal, tissue. More specifically,wire(s) (not shown) may extend from electrosurgical cable 2 (FIG. 1),through housing 20 and shaft 12, ultimately connecting to one or both oftissue sealing plates 112, 122, although other configurations are alsocontemplated. The tissue sealing plates 112, 122 and distal jaw portions111, 121 of one or both of jaw members 110, 120, respectively, cooperateto define a longitudinally-oriented knife channel 125 therein that isconfigured to permit reciprocation of a knife 190 therethrough.

Proximal flanges 113, 123 of jaw members 110, 120, respectively, eachinclude a pivot aperture 114 a, 124 a, respectively, definedtherethrough, and an angled cam slot 114 b, 124 b, respectively, definedtherethrough. End effector assembly 100 also includes a knife guide 170that facilitates alignment and translation of knife 190 through knifechannels 125 upon reciprocation of knife drive rod 193 (FIG. 10). Knifeguide 170 includes first half 170 a and second half 170 b whichmechanically interface to slidably encapsulate the knife 190 therein.First and second halves 170 a and 170 b each include an pivot aperture173 a, 173 b, respectively, defined therethrough and a longitudinal camslot 172 a, 172 b, respectively, defined therethrough. Distal end 16 ofshaft 12 includes a bifurcated portion including first and secondflanges 16 a and 16 b, respectively, that define a channel 16 ctherebetween for receiving jaw members 110 and 120. Each flange 16 a, 16b defines a pivot aperture 17 a, 17 b, respectively, therethrough forreceipt of pivot pin 95, and a longitudinal cam slot 18.

During assembly, pivot pin 95 is inserted through pivot aperture 17 a offlange 16 a of shaft 12, pivot aperture 124 a of proximal flange 123 ofjaw member 120, pivot aperture 173 a of first half 170 a of knife guide170, pivot aperture 173 b of second half 170 b of knife guide 170, pivotaperture 114 a of proximal flange 113 of jaw member 110, and pivotaperture 17 b of flange 16 b of shaft 12 to pivotably engage jaw members110, 120 at distal end 16 of shaft 12. Angled cam slots 114 b, 124 b ofjaw members 110, 120, longitudinal cam slots 172 a, 172 b of first andsecond halves 170 a, 170 b of knife guide 170, and longitudinal camslots 18 of flanges 16 a, 16 b of shaft 12 are configured to receivedrive pin 139, which is engaged to drive sleeve 132 at the distal endthereof. As such, upon translation of drive sleeve 132, drive pin 139 istranslated along slots 114 b, 124 b, 172 a, 172 b, and 18 to pivot jawmembers 110, 120 relative to one another between the spaced-apartposition (FIG. 2A) and the one or more approximated positions (FIG. 2B).

Knife 190 is configured for reciprocation through shaft 12 and knifechannels 125 of jaw members 110, 120, respectively, between a retractedposition, wherein knife 190 is positioned proximally of distal jawportions 111, 121 of jaw members 110, 120, respectively, and one or moreextended positions, wherein knife 190 extends at least partially throughknife channels 125 of jaw members 110, 120 to cut tissue graspedtherebetween. Knife 190 includes a distal blade 191 configured tofacilitate cutting tissue upon translation of knife 190 between jawmembers 110, 120, and a elongated body portion 192. Body portion 192 ofknife 190 defines a longitudinal slot 192 a extending therethrough thatis configured to receive pivot pin 95 and drive pin 139 to permittranslation of knife 190 about pivot pin 95 and drive pin 139. Theproximal end of knife 190 defines one or more pin holes 192 btherethrough for engaging knife 190 to knife drive rod 193 (FIGS.4A-4B), although other engagement configurations are also contemplated.As will be described in greater detail below, knife drive rod 193 (FIGS.4A-4B) is selectively translatable, e.g., upon actuation of trigger 72assembly 70 (FIGS. 4A-4B), through shaft 12 and relative to end effectorassembly 100 to translate knife 190 between the retracted and the one ormore extended positions.

Turning now to FIGS. 4A-4B, in conjunction with FIGS. 1-3, movablehandle 40 includes a lever 42 defining a finger hole 43 and a bifurcatedarm 46 extending upwardly from lever 42 and into housing 20. Arm 46 isbifurcated to define first and second spaced-apart flanges 46 a, 46 b,respectively, that are pivotably coupled to housing 20 at the free endsthereof via pivot pin 45. Flanges 46 a, 46 b extend on either side ofdrive assembly 41 and are coupled thereto to facilitate movement of jawmembers 110, 120 between the spaced-apart position and the one or moreapproximated positions. More specifically, flanges 46 a, 46 b extendupwardly on either side of mandrel 48 and are disposed within lateralslots 49 defined within first and second mandrel components 48 a, 48 b,respectively. First and second mandrel components 48 a, 48 b are engagedto one another about drive sleeve 132, e.g., via snap-fitting or othersuitable engagement, to fixedly engage mandrel 48 about drive sleeve132. Due to this configuration, upon pivoting of movable handle 40 aboutpivot pin 45 and relative to fixed handle 50 from an initial position(FIG. 4A) to one or more compressed positions (FIG. 6), mandrel 48 anddrive sleeve 132 are translated proximally, thereby translating drivepin 132 proximally through angled cam slots 114 b, 124 b of jaw members110, 120, respectively, (and cam slots 18 and 172 a, 172 b of shaft 12and knife guide 170, respectively) to pivot jaw members 110, 120 fromthe spaced-apart position (FIG. 2A) to the one or more approximatedpositions (FIG. 2B). On the other hand, return of movable handle 40towards the initial position returns drive sleeve 132 distally, therebyreturning jaw members 110, 120 towards the spaced-apart position. Aspring 140 is coupled between housing 20 and the proximal end of mandrel48 to bias mandrel 48 distally, thereby biasing movable handle 40towards the initial position and jaw members 110, 120 towards thespaced-apart position. Further, a first control member 150 is engaged tomandrel 48 to, as will be described in greater detail below, selectivelycontrol actuation of trigger assembly 70 in accordance with the relativepositioning of jaw members 110, 120.

Movable handle 40 further includes a latch assembly 180 extendingproximally therefrom. Latch assembly 180 includes a resilient member182, e.g., a flat spring, having a pin 184 engaged at the free endthereof. Upon movement of movable handle 40 from the initial position tothe one or more compressed positions, resilient member 182 is flexed topermit pin 184 to pass over latch member 188 disposed within housing 20.Latch member 188 includes a catch 189 defined therein that is configuredto receive pin 184 for retaining, or latching movable handle 40 in oneor more of the compressed positions and, thus, jaw members 110, 120 inone or more of the approximated positions grasping tissue therebetween.Latch member 188 may further include incremental catches (not explicitlyshown) for latching movable handle 40 at various different positionscorresponding to various different approximated positions of jaw members110, 120, e.g., a first approximated position, wherein jaw members 110,120 define a first gap distance “G” (FIGS. 6A-6B) therebetween, and asecond approximated position, wherein jaw members 110, 120 define asecond, smaller gap distance “g” (FIGS. 7A-7B) therebetween. Otherlatching mechanisms may also be provided.

With continued reference to FIGS. 4A-4B, trigger assembly 70 includes atrigger 72 having a toggle member 73 and a bifurcated arm 76 extendingupwardly from toggle member 73 and into housing 20. Trigger 72 ispivotably coupled to housing 20 via pivot pin 75, which extends throughan intermediate portion 74 of trigger 72. Arm 76 is bifurcated to definefirst and second spaced-apart flanges 76 a, 76 b, respectively, topermit passage of arm 76 about drive assembly 41. A pin 77 extendsbetween flanges 76 a, 76 b at the free ends thereof. A connector rod 78is pivotably coupled to pin 77 at distal end 78 a thereof and is engagedto a base 79 at proximal end 78 b thereof. Base 79, in turn, is engagedto the proximal end of knife drive rod 193, which extends distallytherefrom through drive sleeve 132, ultimately engaging the proximal endof knife 190 (FIG. 3). Accordingly, upon pivoting of trigger 72 aboutpivot pin 75 and relative to housing 20 from an un-actuated position(FIG. 4A) towards one or more actuated positions, flanges 76 a, 76 b andpin 77 are rotated to pull connector rod 78 distally such that knifedrive rod 193 is pushed distally to thereby translate knife 190 from theretracted position towards the one or more extended positions. On theother hand, upon return of trigger 72 towards the un-actuated position,flanges 76 a, 76 b and pin 77 are rotated to push connector rod 78proximally such that knife drive rod 193 is pulled proximally to therebytranslate knife 190 back towards the retracted position. Spring 140,which is disposed about knife drive rod 193 between base 79 and mandrel48 biases base 79 proximally, thereby biasing trigger 72 towards theun-actuated position and knife 190 towards the retracted position.Further, a second control member 160 is engaged to trigger 72 aboutpivot pin 75 to, in conjunction with first control member 150 of driveassembly 41, selectively control actuation of trigger assembly 70 inaccordance with the relative positioning of jaw members 110, 120, aswill be described in greater detail below.

As mentioned above, drive assembly 41 includes a first control member150 coupled to mandrel 48 and trigger assembly 70 includes a secondcontrol member 160 coupled to trigger 72. First control member 150includes a body 152 defining a proximal end 153 having an attachmentmember 154 extending therefrom and a distal end 155 having an engagementleg 156 extending therefrom. Attachment member 154 is configured toengage the proximal end of mandrel 48 such that translation of mandrel48, e.g., upon compression or return of movable handle 40, effectssimilar translation of first control member 150. Housing 20 may includea track (not explicitly shown) defined therein that is configured toguide translation of first control member 150 relative thereto.Engagement leg 156, which extends distally from body 152 of firstcontrol member 150, defines a generally distally-facing angled contactsurface 158.

Second control member 160, as mentioned above, is pivotably engaged totrigger 72 about pivot pin 75. Second control member 160 includes a body162 defining a generally-proximally facing complementary angled contactsurface 168 that is angled similarly to angled contact surface 158 offirst control member 150. First and second control members 150, 160,respectively, and, more particularly, angled contact surface 158 andcomplementary angled surface 168, respectively, thereof, cooperate toselectively control actuation of trigger assembly 70 in accordance withthe relative positioning of jaw members 110, 120. More specifically,first and second control members 150, 160, respectively, are configuredsuch that deployment of knife 190 is prevented when jaw members 110, 120are disposed in the spaced-apart position and such that, when jawmembers 110, 120 are disposed in the one or more approximated positions,the extent to which knife 190 may be deployed is dependent on therelative spacing between first and second jaw members 110, 120,respectively. For example, when jaw members 110, 120 are disposed in afirst approximated position grasping relatively larger-diameter tissuetherebetween such that jaw members 110, 120 are spaced-apart a first gapdistance “G,” trigger 72 may only be actuated so as to translate knife190 to a first extended position, e.g., the position shown in FIGS. 6and 6A-6B. On the other hand, when jaw members 110, 120 are disposed ina second approximated position defining a second gap distance “g”therebetween, e.g., where relatively smaller-diameter tissue is graspedtherebetween, trigger 72 may be actuated to translate knife 190 to asecond extended position, e.g., the position shown in FIGS. 7 and 7A-7B.

Such a feature is advantageous in that the likelihood of knife trap,knife splay, and/or knife mis-alignment is reduced. This is becauseknife 190 is most vulnerable to knife trap, knife splay, and/or knifemis-alignment when jaw members 110, 120 are spaced-apart a relativelygreater distance, e.g., when a relatively smaller portion of knife 190is disposed within knife channels 125 of jaw members 110, 120 thusleaving a larger portion of knife 190 un-guarded (as compared to whenjaw members 110, 120 are closer-together, thus allowing a greaterportion of knife 190 to be disposed within and guarded by knife channels125) and when knife 190 is further extended between jaw members 110, 120(as compared to when only a small portion of knife 190 extends betweenjaw members 110, 120). Thus, by regulating the extent to which knife 190can be deployed as a function of the gap distance between jaw members110, 120, the most vulnerable situations where knife trap, knife splay,and/or knife mis-alignment may occur, e.g., where only a relativelysmall portion of knife 190 is disposed within knife channels 125 andwhere a greater portion of knife 190 is extended between jaw members110, 120, can be avoided. The cooperating features of first controlmember 150 of drive assembly 41 and second control member 160 of triggerassembly 70 which interact to regulate deployment of knife 190 willbecome more apparent below in view of the description of the use andoperation of forceps 10.

The use and operation of forceps 10 for grasping, treating, and/ordividing various different tissues and/or performing various differenttissue treatments is described with reference to FIGS. 1-7B. Referringinitially to FIG. 5, in conjunction with FIGS. 1-4B, with jaw members110, 120 disposed in the spaced-apart position, forceps 10 ismanipulated and/or maneuvered into position such that tissue to begrasped, treated, and/or divided in disposed between jaw members 110,120. At this point, movable handle 40 is disposed in the initialposition and trigger 72 is disposed in the un-actuated position suchthat knife 190 is disposed in the retracted position. With movablehandle 40 disposed in the initial position, mandrel 48 is positioned isa more-distal position and, thus, first control member 150 is likewisepositioned in a more-distal, or initial position “P₀.” In the initialposition of first control member 150, angled surface 158 abutscomplementary angled surface 168 of second control member 160 of trigger72, preventing actuation of trigger 72. As such, knife 190 is maintainedin the retracted position when jaw members 110, 120 are disposed in thespaced-apart position.

With reference now to FIGS. 6 and 6A-6B, in conjunction with FIGS. 1-4B,in order to grasp, treat, and/or divide relatively large-diametertissue, relatively less compressible tissue, for procedures where alarger gap distance is desired, and/or for procedures where a lesserclosure pressure is desired, movable handle 40 is compressed, or pulledproximally relative to fixed handle 50 from the initial position to afirst compressed position such that jaw members 110, 120 are pivotedrelative to one another to the first approximated position to grasptissue therebetween. More specifically, as movable handle 40 iscompressed, mandrel 48 and drive sleeve 132 are translated proximally,thus pulling jaw members 110, 120 to pivot towards one another to thefirst approximated position, wherein jaw members 110, 120 define a gapdistance “G” therebetween. Jaw members 110, 120 may be approximated to aparticular position, e.g., the first approximated position, to achieve adesired closure pressure on tissue, or until a particular latchingposition is achieved, e.g., via engagement of latch assembly 180 (FIGS.4A-4B) at a particular position. The proximal translation of mandrel 48also effects proximal translation of first control member 150 from theinitial position “P₀” to a first proximal position “P₁,” wherein firstcontrol member 150 is spaced-apart from second control member 160 adistance “x₁.”

With jaw members 110, 120 grasping tissue between tissue sealing plates112, 122, respectively, thereof, tissue sealing plate 112 and/or tissuesealing plate 122 may be energized, e.g., via actuation of one or bothof switches 62, 64 of switch assembly 60 (FIG. 1), to conduct energybetween tissue sealing plates 112, 122 and through tissue to treat,e.g., seal, tissue.

At the completion of tissue treatment, or where it is only desired tocut tissue, trigger 72 may be actuated to cut tissue grasped between jawmembers 110, 120. Since first control member 150 is disposed in thefirst proximal position “P₁” a distance “x₁” from second control member160, trigger 72 may be partially actuated, e.g., to translate secondcontrol member 160 the distance “x₁.” More specifically, trigger 72 maybe actuated from the un-actuated position to a first actuated position,until complementary angled surface 168 of second control member 160 ismoved the distance “x₁” to abut angled surface 158 of first controlmember 150, thereby preventing further actuation of trigger 72. Astrigger 72 is actuated, connector rod 78 and knife drive rod 193 arepulled distally, thereby urging knife 190 from the retracted position tothe first extended position wherein, as shown in FIG. 6B, knife 190extends partially between jaw members 110, 120, to position “k₁,” to cuttissue grasped therebetween. Knife 190 is prevented from furthertranslation through knife channels 125 and between jaw members 110, 120due to the abutment of angled surface 158 of first control member 150and complementary angled surface 168 of second control member 160. Asmentioned above, this feature protects knife 190 by preventing knife 190from being further extended in a situation where a relatively smallerportion of knife 190 is disposed within and guided by knife channels 125of jaw members 110, 120 (due to the relatively larger gap distance “G”between jaw members 110, 120).

Once tissue has been cut, knife 190 is retracted, e.g., via releasingtrigger 72 and allowing trigger 72 to return under bias to theun-actuated position. Thereafter, movable handle 40 is unlatched and/orreleased and is returned to the initial position to return jaw members110, 120 to the spaced-apart position to release the treated and dividedtissue.

Turning now to FIGS. 7 and 7A-7B, in conjunction with FIGS. 1-4B, theuse and operation of forceps 10 for grasping, treating, and/or dividingrelatively small-diameter tissue, relatively more compressible tissue,for procedures where a smaller gap distance is desired, and/or forprocedures where a greater closure pressure is desired, is substantiallysimilar to that described above with respect to FIGS. 6 and 6A-6B and,thus, only the differences therebetween will be described in detailwhile similarities will be only summarily described or omitted entirelyfor purposes of brevity.

Initially, to grasp tissue, movable handle 40 is compressed towardsfixed handle 50 from the initial position, past the first compressedposition, to a second compressed position such that jaw members 110, 120are pivoted relative to one another to the second approximated positionto grasp tissue therebetween and define a relatively smaller gapdistance “g” therebetween. Movement of movable handle 40 to the secondcompressed position effects proximal translation of mandrel 48 and drivesleeve 132 to approximate jaw members 110, 120 and also effects proximaltranslation of first control member 150 from the initial position “P₀,”past the first proximal position “P₁” (FIG. 6), to a second proximalposition “P₂,” wherein first control member 150 is spaced-apart fromsecond control member 160 a distance “x₂.” Thereafter, with tissuegrasped between tissue sealing plates 112, 122 of jaw members 110, 120,respectively, energy may be conducted between tissue sealing plates 112,122 and through tissue to treat, e.g., seal, tissue.

At the completion of tissue treatment, or where it is only desired tocut tissue, trigger 72 may be actuated to cut tissue grasped between jawmembers 110, 120. Since first control member 150 is disposed in thesecond proximal position “P₂” a distance “x₂” from second control member160, trigger 72 may be actuated further as compared to when jaw members110, 120 are further spaced-apart. That is, trigger 72 may be actuatedfrom the un-actuated position, past the first actuated position, to asecond actuated position, wherein second control member 160 is moved thedistance “x₂” until complementary angled surface 168 of second controlmember 160 contacts angled surface 158 of first control member 150 toprevent further actuation of trigger 72. This relatively greater, orfurther actuation of trigger 72 corresponds to relatively greater distaltranslation of connector rod 78 and knife drive rod 193 and, thus,relatively further extension of knife 190 between jaw members 110, 120to position “k₂,” as shown in FIG. 7B, to cut tissue graspedtherebetween.

At this point, knife 190 is prevented from further translation throughknife channels 125 and between jaw members 110, 120 due to the abutmentof angled surface 158 of first control member 150 and complementaryangled surface 168 of second control member 160. However, in thisposition, knife 190 has been extended further relative to situationswherein jaw members 110, 120 are spaced-apart a greater distance, e.g.,as in FIGS. 6 and 6A-6B wherein jaw members 110, 120 define gap distance“G” therebetween, since a relatively greater portion of knife 190 isdisposed within and guided by knife channels 125 of jaw members 110,120, thereby providing greater protection from knife trap, knife splay,and/or knife mis-alignment. Once tissue has been cut, knife 190 isretracted and jaw members 110, 120 are returned to the spaced-apartposition to release the treated and divided tissue.

Turning now to FIG. 8, another embodiment of a forceps 200 similar toforceps 10 (FIG. 1) is shown. Forceps 200 is similar to forceps 10(FIG. 1) except for the configuration and operation of first controlmember 250 of drive assembly 241 and second control member 260 oftrigger assembly 270. Thus, only these differences will be describedbelow to avoid unnecessary repetition.

With continued reference to FIG. 8, drive assembly 241 of forceps 200includes a first control member 250 and trigger assembly 270 of forceps200 includes a second control member 260. First control member 250includes a body 252 defining a proximal end 253 having a proximal finger254 extending therefrom and a distal end 255 having an engagement leg256 extending therefrom. Engagement leg 256 of first control member 250,which extends distally from body 252, defines a generallydistally-facing angled contact surface 258. First control member 250 isbiased distally via a spring 280 coupled between distal end 255 of firstcontrol member 250 and housing 222. Proximal finger 254 is positionedadjacent to and proximally of mandrel 248 of drive assembly 241 suchthat, upon proximal translation of mandrel 248, e.g., upon compressionof movable handle 240, mandrel 248 urges first control member 250proximally. Upon distal translation of mandrel 248, e.g., upon return ofmovable handle 240, spring 280 biases first control member 250 distallyto maintain proximal finger 254 of first control member 250 in abutmentwith mandrel 248.

Second control member 260, similar to second control member 160 oftrigger assembly 70 of forceps 10 (see FIGS. 1-7B), is pivotably engagedto trigger 272. Second control member 260 includes a body 262 defining agenerally-proximally facing complementary angled contact surface 268that is angled similarly to angled contact surface 258 of first controlmember 250.

In use, first and second control members 250, 260, respectively, offorceps 200 function similar to first and second control members 150,160, respectively, of forceps 10 (see FIGS. 1-7B). However, rather thanpreventing actuation of trigger 272 beyond a particular position, firstand second control members 250, 260, respectively, provide addedresistance and/or feedback, e.g., tactile and/or audible feedback, tothe user once trigger 272 has reached the particular position,indicating to the user that the knife 190 (FIG. 3) has been extended tothe particular position or is approaching the particular positionwherein the knife 190 (FIG. 3) may be vulnerable to knife trap, knifesplay, and/or knife mis-alignment. For example, when movable handle 240is disposed in the initial position, mandrel 248 is positioned is amore-distal position and, thus, first control member 250 is likewisepositioned in a more-distal, or initial position. Further, in thisposition, jaw members 210, 220 are disposed in the spaced-apartposition. In the initial position of first control member 250, angledsurface 258 of first control member 250 abuts complementary angledsurface 268 of second control member 260. Thus, upon actuation oftrigger 272, the user would encounter added resistance in actuatingtrigger 272 as complementary angled surface 268 contacts angled surface258 to urge first control member 250 proximally against the bias ofspring 280. This added resistance is felt tactilely by the user.

On the other hand, when movable handle 240 is moved to the firstcompressed position such that jaw members 210, 220 are disposed in thefirst approximated position, first control member 250 is movedproximally under the urging of mandrel 248 to a first proximal position.In this position, upon actuation of trigger 272, the user would be ableto more-freely actuate trigger 272 from the un-actuated position to thefirst actuated position, but would encounter added resistance uponactuation beyond the first actuated position as complementary angledsurface 268 contacts angled surface 258 to urge first control member 250proximally against the bias of spring 280. Thus, the user would betactilely alerted as to the extent of deployment of knife 190 (FIG. 3).First and second control members 250, 260, respectively, functionsimilarly with respect to second, third, etc., compressed positions ofmovable handle 240.

Angled surface 258 and complementary angled surface 268 of first andsecond control members 250, 260, respectively, may further includeteeth, serrations, or other suitable features (not explicitly shown)configured to engage one another upon contact of surfaces 250 and 260,thereby also providing audible feedback to the user. For example, angledteeth would produce “clicking” audible feedback signals as the teeth ofsurfaces 250, 260 slide in contact with one another upon furtheractuation of trigger 272 beyond the particular position. The teeth mayincrease in size, rigidity and/or configuration along the length ofsurfaces 250, 260 such that a greater audible feedback signal isproduced as trigger 272 is actuated further beyond the particularposition. Other configurations may also be provided.

Turning now to FIGS. 9-10, another embodiment of a forceps provided inaccordance with the present disclosure is shown generally identified byreference numeral 300. Forceps 300 is similar to forceps 10 (FIG. 1)except for the control member 350 thereof. Thus, only these differenceswill be described in detail below, while similarities will be onlysummarily described or omitted entirely for purposes of brevity.

Forceps 300 includes a movable handle 340 having a lever 342 pivotablycoupled to housing 322 via pivot pin 345 and engaged to mandrel 348 suchthat pivoting of movable handle 340 between an initial position (FIG. 9)and one or more compressed positions (FIG. 10) translates mandrel 348and drive sleeve 332 proximally, thereby moving the jaw members 110, 120(FIGS. 2A-2B) relative to one another from the spaced-apart position(FIG. 2A) to the one or more approximated positions (FIG. 2B). Triggerassembly 370 includes a trigger 372 pivotably coupled to housing 322 viapivot pin 375, a connector rod 378 pivotably coupled to trigger 372 atdistal end 378 a thereof, and a base 379 coupled to proximal end 378 bof connector rod 378 and to knife drive rod 393 such that, uponactuation of trigger 372, connector rod 378 and base 379 are moved totranslate knife drive rod 393, to thereby translate knife 190 (FIG. 3)between the retracted position and the one or more extended positions.

Control member 350 of forceps 300 defines an elongated body 352 having aproximal end 353, a distal end 355 that is pivotably or flexibly coupledto mandrel 348, and a plurality of spaced-apart protrusions, e.g.,first, second, third and fourth protrusions 358 a, 358 b, 358 c, 358 d,respectively, although greater or fewer protrusions may be provided,extending therefrom along at least a portion of the length thereof.Control member 350 further includes an attachment arm 360 extendingtherefrom that is coupled to housing 322 via a slot-aperture engagement362, allowing attachment arm 360 and, thus, elongated body 352 to rotateat least partially relative to housing 322 and to translate relative tohousing 322 along the length of the slot of slot-aperture engagement362. As will be described in greater detail below, control member 350operates so as to regulate the deployment of knife 190 (FIG. 3) as afunction of the relative spacing between first and second jaw members110, 120, respectively (FIGS. 2A-2B), e.g., to prevent deployment ofknife 190 (FIG. 3) beyond a particular position that is dependent on thespacing between jaw members 110, 120 (FIGS. 2A-2B) and/or to provideadded resistance and tactile and/or audible feedback to the user as towhen the knife 190 (FIG. 3) is approaching, has been deployed to, orextends beyond, the particular position.

With reference to FIG. 9, forceps 300 is shown wherein movable handle340 is disposed in the initial position (such that jaw members 110, 120(FIGS. 2A-2B) are disposed in the spaced-apart position) and trigger 372is disposed in the un-actuated position (such that knife 190 (FIG. 3) isdisposed in the retracted position). In this position, mandrel 348 ispositioned is a more-distal position and, thus, control member 350 ispositioned such that first protrusion 358 a is positioned distally ofand in abutment with base 379. First protrusion 358 a (and/or the otherprotrusions 358 b, 358 c, 358 d) may be formed from a rigid materialsuch that deployment of trigger 372 is prevented in this position or,alternatively, first protrusion 358 a (and/or the other protrusions 358b, 358 c, 358 d) may be formed from a resiliently flexible material suchthat, in order to actuate trigger 372, the user must provide sufficientforce to deflect first protrusion 358 a. The resistance to deflection offirst protrusion 358 a provides added resistance to actuation of trigger372, thus providing tactile feedback to the user. Teeth or otherfeatures (not explicitly shown) on either or both of first protrusion358 a (or any of the other protrusions) and base 379 may be provided foradditionally providing audible feedback to the user. As can beappreciated, control member 350, similar to the embodiments above,prevents and/or alerts the user as to when trigger 372 is beingactuated, has been actuated, or is attempting to be actuated, when jawmembers 110, 120 (FIGS. 2A-2B) are disposed in the spaced-apartposition.

Referring to FIG. 10, when movable handle 340 is compressed, or pulledproximally to a compressed position (e.g., a first compressed position,a second compressed position, etc.) to move jaw members 110, 120 (FIGS.2A-2B) to an approximated position (e.g., a first approximated position,a second approximated position, etc.) to grasp tissue therebetween,mandrel 348 is translated proximally, thus urging control member 350 torotate and translate in a generally downward direction to the positionshown in FIG. 10. The extent of compression of movable handle 340, e.g.,whether movable handle 340 is compressed to the first compressedposition, the second compressed position, etc., and, thus, the extent ofapproximation of jaw members 110, 120 (FIGS. 2A-2B), e.g., whether jawmembers 110, 120 are moved to the first approximated position, thesecond approximated position, etc., determines the positioning ofcontrol member 350 relative to housing 322 and base 379. As shown inFIG. 10, control member 350 has been moved, e.g., to a second compressedposition, such that first and second protrusions 358 a, 358 b,respectively, no longer interfere with base 379. Thus, trigger 372 maybe actuated to translate base 379 and knife drive rod 393 distally,thereby extending knife 190 (FIG. 3) between jaw members 110, 120 (FIGS.2A-2B), e.g., to a second extended position, until base 379 contactsthird protrusion 358 c. Thereafter, trigger 372 may be prevented fromfurther actuation due to the interference between third protrusion 358 cand base 379 (in embodiments where third protrusion 358 c is rigid) or,alternatively, tactile and/or audible feedback may be provided and theuser may be required to apply additional force to further actuatetrigger 372 (in embodiments where third protrusion 358 c is resilientlyflexible). As can be appreciated, the spacing of protrusions 358 a, 358b, 358 c, 358 d and/or configuration of control member 350 may otherwisebe configured so as to control deployment of knife 190 (FIG. 3) inaccordance with the gap distance between jaw members 110, 120, asdesired.

While several embodiments of the disclosure have been shown in thedrawings, it is not intended that the disclosure be limited thereto, asit is intended that the disclosure be as broad in scope as the art willallow and that the specification be read likewise. Therefore, the abovedescription should not be construed as limiting, but merely asexemplifications of particular embodiments. Those skilled in the artwill envision other modifications within the scope and spirit of theclaims appended hereto.

What is claimed is:
 1. A surgical instrument, comprising: a housing; anend effector assembly distally-spaced from the housing, the end effectorassembly having first and second jaw members, at least one of the firstor second jaw members movable relative to the other between aspaced-apart position and an approximated position; a knife selectivelymovable relative to the end effector assembly between a retractedposition and an extended position; a trigger pivotably coupled to thehousing and operably coupled to the knife, the trigger selectivelyactuatable relative to the housing from an un-actuated position to anactuated position to move the knife from the retracted position to theextended position, the trigger defining a first control surface; and asecond control surface movably disposed within the housing and operablyassociated with the end effector assembly, wherein: when the at leastone of the first or second jaw members is disposed in the spaced-apartposition, the second control surface is positioned to interfere with thefirst control surface to prevent actuation of the trigger from theun-actuated position, thereby preventing movement of the knife from theretracted position, when the at least one of the first or second jawmembers is disposed in the approximated position, the second controlsurface is positioned to permit actuation of the trigger from theun-actuated position to the actuated position to move the knife from theretracted position to the extended position, and when the at least oneof the first or second jaw members is disposed in an intermediateposition between the spaced-apart position and the approximatedposition, the second control surface is positioned: to permit actuationof the trigger from the un-actuated position to anintermediately-actuated position between the un-actuated position andthe actuated position, thereby permitting the knife to move from theretracted position to a partially-extended position between theretracted position and the extended position, and to interfere with thefirst control surface to prevent actuation of the trigger beyond theintermediately-actuated position, thereby preventing movement of theknife beyond the partially-extended position.
 2. The surgical instrumentaccording to claim 1, further comprising a shaft extending between thehousing and the end effector assembly, wherein the knife is slidablydisposed within the shaft.
 3. The surgical instrument according to claim1, further comprising a drive assembly coupled to the at least one ofthe first or second jaw members, the drive assembly selectivelyactuatable for moving the at least one of the first or second jawmembers between the spaced-apart and approximated positions.
 4. Thesurgical instrument according to claim 3, further comprising a movablehandle operably coupled to the drive assembly, the movable handleselectively actuatable between an initial position and a compressedposition for actuating the drive assembly to thereby move the at leastone of the first or second jaw members between the spaced-apart positionand the approximated position.
 5. The surgical instrument according toclaim 4, wherein movement of the movable handle effects movement of thesecond control surface relative to the housing.
 6. The surgicalinstrument according to claim 1, further comprising a movable handleoperably coupled to end effector assembly, the movable handleselectively actuatable between an initial position and a compressedposition for moving the at least one of the first or second jaw membersbetween the spaced-apart position and the approximated position.
 7. Thesurgical instrument according to claim 6, wherein movement of themovable handle effects movement of the second control surface relativeto the housing.
 8. The surgical instrument according to claim 6, furthercomprising a latch assembly operably associated with the housing and themovable handle, the latch assembly configured to releasably latch themovable handle in the compressed position.
 9. The surgical instrumentaccording to claim 1, wherein at least one of the first or second jawmembers includes a knife channel defined therein, the knife channelconfigured to permit reciprocation of the knife therethrough.
 10. Thesurgical instrument according to claim 1, wherein at least one of thefirst or second jaw members is adapted to connect to a source ofelectrosurgical energy.
 11. A surgical instrument, comprising: ahousing; an end effector assembly distally-spaced from the housing, theend effector assembly having first and second jaw members, at least oneof the first or second jaw members movable relative to the other betweena spaced-apart position and an approximated position; a knifeselectively movable relative to the end effector assembly between aretracted position and an extended position; a trigger pivotably coupledto the housing and operably coupled to the knife, the triggerselectively actuatable relative to the housing from an un-actuatedposition to an actuated position to move the knife from the retractedposition to the extended position, the trigger defining a first controlsurface; and a second control surface movably disposed within thehousing and operably associated with the end effector assembly, wherein:when the at least one of the first or second jaw members is disposed inthe spaced-apart position, the second control surface is positioned tointerfere with the first control surface to provide additionalresistance to actuation of the trigger from the un-actuated position,when the at least one of the first or second jaw members is disposed inthe approximated position, the second control surface is positioned topermit actuation of the trigger from the un-actuated position to theactuated position without additional resistance, and when the at leastone of the first or second jaw members is disposed in an intermediateposition between the spaced-apart position and the approximatedposition, the second control surface is positioned: to permit actuationof the trigger from the un-actuated position to anintermediately-actuated position between the un-actuated position andthe actuated position without additional resistance, and to interferewith the first control surface to provide additional resistance toactuation of the trigger beyond the intermediately-actuated position.12. The surgical instrument according to claim 11, further comprising ashaft extending between the housing and the end effector assembly,wherein the knife is slidably disposed within the shaft.
 13. Thesurgical instrument according to claim 11, further comprising a driveassembly coupled to the at least one of the first or second jaw members,the drive assembly selectively actuatable for moving the at least one ofthe first or second jaw members between the spaced-apart andapproximated positions.
 14. The surgical instrument according to claim13, further comprising a movable handle operably coupled to the driveassembly, the movable handle selectively actuatable between an initialposition and a compressed position for actuating the drive assembly tothereby move the at least one of the first or second jaw members betweenthe spaced-apart position and the approximated position.
 15. Thesurgical instrument according to claim 14, wherein movement of themovable handle effects movement of the second control surface relativeto the housing.
 16. The surgical instrument according to claim 11,further comprising a movable handle operably coupled to end effectorassembly, the movable handle selectively actuatable between an initialposition and a compressed position for moving the at least one of thefirst or second jaw members between the spaced-apart position and theapproximated position.
 17. The surgical instrument according to claim16, wherein movement of the movable handle effects movement of thesecond control surface relative to the housing.
 18. The surgicalinstrument according to claim 16, further comprising a latch assemblyoperably associated with the housing and the movable handle, the latchassembly configured to releasably latch the movable handle in thecompressed position.
 19. The surgical instrument according to claim 11,wherein at least one of the first or second jaw members includes a knifechannel defined therein, the knife channel configured to permitreciprocation of the knife therethrough.
 20. The surgical instrumentaccording to claim 11, wherein at least one of the first or second jawmembers is adapted to connect to a source of electrosurgical energy.